Cooling System problems

1973Mach1 · 06-18-1999, 10:07 PM

I recently bought a 1973 Ford Mustang Mach I, with a rebuilt 351 Cleveland. There several strange occurrences within the cooling system, most likely all related in someway.
First, when the engine starts to get warm, and you step on the gas, the top radiator hose collapses completely. Next, when we attempt to run the engine without the radiator cap (as all the manuals say is
possible), the coolant first goes down and appears to be circulating, but then it will quickly rise up and begin to overflow. Most
mysterious of all, when the coolant is overflowing, if the engine is shut off, the coolant is forced out of the radiator so quickly that it gushes a stream the diameter of the cap at least a foot out of the radiator. (Also, the engine never overheats when it does these things, the gauge reads in the bottom quarter or less, and the thermostat does open)
In order to correct these problems, I have tried at least five different thermostat, of both the low temp. and the high temp., as well as even drilling a small hole in the thermostat like the older ones
used to. Also, we tried replacing the radiator, the hoses and even the cap, and still the problem persists. Lastly, I removed the water pump and it appeared normal, spun cleanly, and showed no signs of corrosion.
Any help you could give us as to why all of these problems occur would be appreciated.

mslcr · 06-19-1999, 12:49 AM

In order to collapse a hose, you must be "pulling a vacuum" on it. Also, since water is non-compressable...there must be a large pocket of air in the system(which of course IS compressable). This must also be the energy released that causes the gusher when the pump stops turning. Now, I think you need a way to purge the air from the system!
Hope this helps.

MEDIK418 · 06-22-1999, 04:53 AM

Who in the world said you could run a car without a radiator cap? Water which makes up about half of your coolant mixture boils at 212 degrees. Coolant Temperatures inside your engine often exceed 212 degrees as it moves toward the radiator. Increased pressure raises the boiling point of any liquid. Your radiator cap allows 6-8 psi of pressure to build in the cooling system thus preventing boilover from too high temperatures. As the water in your cooling system is heating it is expanding. As for the gushing water, as long as the engine is running the water pump is applying pressure to the water in the block as it pushes against the thermostat. Shut down the water pump and the pressure goes to zero and all that water which is at 212 degrees or higher boils. Water expands at a rate of 1700 to one when it boils so when it boils inside the cooling system the remaining water has to go somewhere. As for the top hose collapsing, it's possible the coolant being pulled into the engine is pulling a vacume on the radiator that shows up in the top hose. You didn't mention whether the engine was overheating or not. I'd suggest trying a new radiator cap first.

Clark Rodgers · 06-22-1999, 09:43 AM

I guess the last response didn't read that you have already changed the cap. I had a 68 coupe that had some of the same problems that you are seeing and it turned out to be the water pump. I know you said it turns and looks fine but on this car it took four different pumps to fix my problem. These obviously some cheap pumps I was using but it just shows that some work different than others even when they look fine. You've obviously tried quite a few things but I think this is your best shot. One more thing, you might consider changing that temp. sending unit also, mine always showed cool even when the car was boiling over !

MEDIK418 · 06-22-1999, 07:33 PM

Woops! You are absolutely correct on that one, I flat didn't see that about the cap. I was zero'd in on him running without the radiator cap. My apologies. Someone years ago gaver me some rather bad advice about running without a cap and I almost lost an engine. Anyway, I've had the same problem with my 71 cleveland and it turned out to be a pressure problem. The gauge indicated hot and all that it needed was a new cap to stop the boilover and a new sending unit to correct the nonexistant overheating problem. But please, never run without a good radiator cap. It may cause cylinder cavitation problems that will destroy your engine.

------------------
Father to two Teenage boys and three Mustangs. 71 Mach 1, 85 LX trunk, and one '89 GT
Someday. . . It's gonna be Dad's turn to build one.

1973Mach1 · 06-23-1999, 08:38 PM

I would like to make it clear that I do have a good sized collection of knowledge on Mustangs. So in answer to two of the posts, I would like to say that back in the muscle era of cars, it was quite common to run without a radiator cap. In fact, in both the owners manual, and the shop manual, it is reccommended to fill the coolant system and then run the car withOUT the cap on, this way easily allowing the air out. Also, as long as the water is being circulated by the pump, their is no need for the cap to be on, it used to be that you could leave the cap off and put a thermometer in the coolant, and it was possible to tell when the thermostat opened due to the temperature change. Further, I did mention that the engine did not overheat(the coolant that gushes out is room temperature or less), and as was already pointed out, the cap has been replaced.
To the other user who posted: I just replaced the water pump with a new one, and the problems are stilll there. The only thing left to do is pull the heads, and see if something is amiss beneath them.

MEDIK418 · 06-24-1999, 10:30 PM

I meant not to upset anyone and I'm sure you know more about Mustangs than I do but I grew up in the muscle car era and running without a radiator cap on those high compressoin motors for a couple of blocks would cause the cooling system to belch out everything in it. But, I shan't argue. I would imagine you're right on about pulling the heads. Blown head gaskets can air up a radiator in a hurry. I'm curious to see what you find.
Good luck.

------------------
Father to two Teenage boys and three Mustangs. 71 Mach 1, 85 LX trunk, and one '89 GT
Someday. . . It's gonna be Dad's turn to build one.

1973Mach1 · 06-25-1999, 10:33 PM

Well, I only have one head off and I already see what my problem was. The guy I had purchased the Mustang from had rebuilt the 351C that is in it currently. However, even though the head gasket is clearly labeled, it was installed BACKWARD! By doing this, it completely blocked off one of the water jacket holes from the block into the heads. I can only imagine that the other head is similarly affected. At least now I know what exactly causes these types of problems, and will hopefully be able to tell anyone else in the future. Thanks for all your help.

06-18-1999, 10:07 PM	#1
1973Mach1 Registered Member Join Date: Jun 1999 Location: Canton, New York, USA Posts: 4	Cooling System problems I recently bought a 1973 Ford Mustang Mach I, with a rebuilt 351 Cleveland. There several strange occurrences within the cooling system, most likely all related in someway. First, when the engine starts to get warm, and you step on the gas, the top radiator hose collapses completely. Next, when we attempt to run the engine without the radiator cap (as all the manuals say is possible), the coolant first goes down and appears to be circulating, but then it will quickly rise up and begin to overflow. Most mysterious of all, when the coolant is overflowing, if the engine is shut off, the coolant is forced out of the radiator so quickly that it gushes a stream the diameter of the cap at least a foot out of the radiator. (Also, the engine never overheats when it does these things, the gauge reads in the bottom quarter or less, and the thermostat does open) In order to correct these problems, I have tried at least five different thermostat, of both the low temp. and the high temp., as well as even drilling a small hole in the thermostat like the older ones used to. Also, we tried replacing the radiator, the hoses and even the cap, and still the problem persists. Lastly, I removed the water pump and it appeared normal, spun cleanly, and showed no signs of corrosion. Any help you could give us as to why all of these problems occur would be appreciated.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
NEED HELP!!, cooling system problem	TRICK_5_0	Windsor Power	2	08-21-2003 10:02 AM
Cooling system not building pressure	Falcons Talon	Windsor Power	5	10-12-2002 09:29 AM
Cooling Problems and Possible Upgrades?	KobraLX	Windsor Power	7	07-01-2002 11:57 AM
How to clean cooling system???	Fostang	Windsor Power	1	07-15-2001 06:13 AM
Cooling System	z_herbst	Windsor Power	23	04-18-2001 11:48 AM

06-19-1999, 12:49 AM	#2
mslcr Registered Member Join Date: Mar 1999 Location: WY Posts: 41	In order to collapse a hose, you must be "pulling a vacuum" on it. Also, since water is non-compressable...there must be a large pocket of air in the system(which of course IS compressable). This must also be the energy released that causes the gusher when the pump stops turning. Now, I think you need a way to purge the air from the system! Hope this helps.

06-22-1999, 04:53 AM	#3
MEDIK418 Registered Member Join Date: Mar 1999 Location: Amarillo, Texas, USA Posts: 780	Who in the world said you could run a car without a radiator cap? Water which makes up about half of your coolant mixture boils at 212 degrees. Coolant Temperatures inside your engine often exceed 212 degrees as it moves toward the radiator. Increased pressure raises the boiling point of any liquid. Your radiator cap allows 6-8 psi of pressure to build in the cooling system thus preventing boilover from too high temperatures. As the water in your cooling system is heating it is expanding. As for the gushing water, as long as the engine is running the water pump is applying pressure to the water in the block as it pushes against the thermostat. Shut down the water pump and the pressure goes to zero and all that water which is at 212 degrees or higher boils. Water expands at a rate of 1700 to one when it boils so when it boils inside the cooling system the remaining water has to go somewhere. As for the top hose collapsing, it's possible the coolant being pulled into the engine is pulling a vacume on the radiator that shows up in the top hose. You didn't mention whether the engine was overheating or not. I'd suggest trying a new radiator cap first.

06-22-1999, 09:43 AM	#4
Clark Rodgers Registered Member Join Date: May 1999 Location: Rowlett,Texas Posts: 306	I guess the last response didn't read that you have already changed the cap. I had a 68 coupe that had some of the same problems that you are seeing and it turned out to be the water pump. I know you said it turns and looks fine but on this car it took four different pumps to fix my problem. These obviously some cheap pumps I was using but it just shows that some work different than others even when they look fine. You've obviously tried quite a few things but I think this is your best shot. One more thing, you might consider changing that temp. sending unit also, mine always showed cool even when the car was boiling over !

06-22-1999, 07:33 PM	#5
MEDIK418 Registered Member Join Date: Mar 1999 Location: Amarillo, Texas, USA Posts: 780	Woops! You are absolutely correct on that one, I flat didn't see that about the cap. I was zero'd in on him running without the radiator cap. My apologies. Someone years ago gaver me some rather bad advice about running without a cap and I almost lost an engine. Anyway, I've had the same problem with my 71 cleveland and it turned out to be a pressure problem. The gauge indicated hot and all that it needed was a new cap to stop the boilover and a new sending unit to correct the nonexistant overheating problem. But please, never run without a good radiator cap. It may cause cylinder cavitation problems that will destroy your engine. ------------------ Father to two Teenage boys and three Mustangs. 71 Mach 1, 85 LX trunk, and one '89 GT Someday. . . It's gonna be Dad's turn to build one.

06-23-1999, 08:38 PM	#6
1973Mach1 Registered Member Join Date: Jun 1999 Location: Canton, New York, USA Posts: 4	I would like to make it clear that I do have a good sized collection of knowledge on Mustangs. So in answer to two of the posts, I would like to say that back in the muscle era of cars, it was quite common to run without a radiator cap. In fact, in both the owners manual, and the shop manual, it is reccommended to fill the coolant system and then run the car withOUT the cap on, this way easily allowing the air out. Also, as long as the water is being circulated by the pump, their is no need for the cap to be on, it used to be that you could leave the cap off and put a thermometer in the coolant, and it was possible to tell when the thermostat opened due to the temperature change. Further, I did mention that the engine did not overheat(the coolant that gushes out is room temperature or less), and as was already pointed out, the cap has been replaced. To the other user who posted: I just replaced the water pump with a new one, and the problems are stilll there. The only thing left to do is pull the heads, and see if something is amiss beneath them.

06-24-1999, 10:30 PM	#7
MEDIK418 Registered Member Join Date: Mar 1999 Location: Amarillo, Texas, USA Posts: 780	I meant not to upset anyone and I'm sure you know more about Mustangs than I do but I grew up in the muscle car era and running without a radiator cap on those high compressoin motors for a couple of blocks would cause the cooling system to belch out everything in it. But, I shan't argue. I would imagine you're right on about pulling the heads. Blown head gaskets can air up a radiator in a hurry. I'm curious to see what you find. Good luck. ------------------ Father to two Teenage boys and three Mustangs. 71 Mach 1, 85 LX trunk, and one '89 GT Someday. . . It's gonna be Dad's turn to build one.

06-25-1999, 10:33 PM	#8
1973Mach1 Registered Member Join Date: Jun 1999 Location: Canton, New York, USA Posts: 4	Well, I only have one head off and I already see what my problem was. The guy I had purchased the Mustang from had rebuilt the 351C that is in it currently. However, even though the head gasket is clearly labeled, it was installed BACKWARD! By doing this, it completely blocked off one of the water jacket holes from the block into the heads. I can only imagine that the other head is similarly affected. At least now I know what exactly causes these types of problems, and will hopefully be able to tell anyone else in the future. Thanks for all your help.